Further studies on the development of sodium channel proteins from rat brain were carried out. By using neurotoxins specific for different parts of the sodium channel protein, we found that the sodium channel protein undergoes conformational changes during development. In early stages of development, we found two 125I-scorpion toxin sites per 3H-saxitoxin site, whereas at later stages of development, the stochiometry of these two sites had changed to two 3H-saxitoxin sites per 125I-scorpion toxin site. Despite this changing stochiometry, both forms of this protein behaved identically on lectin affinity columns, ion exchange columns and on SDS-polyacrylamide gel electrophoresis, suggesting that no biochemical differences were detectable. In another project, muscarinic receptor protein from rat brain was partially purified using preparative isoelectric focusing, lectin affinity chromatography and gel permeation chromatography. This affinity labeled protein binds to, and can be specifically eluted from wheat germ affinity columns and has a molecular weight of 80,000 daltons and an isoelectric point of 5.9.